Several fan groups and bloggers have called for change at the club and Emery said the Gunners are being "very demanding" with their transfer targets, BBC Sport reported.
They have already had bids rejected for Crystal Palace winger Wilfried Zaha and Celtic left-back Kieran Tierney.
"Our target is to achieve three or four players who really improve our team and our squad now," said Emery.
"We have very good players and very good young players who can progress to take and get big performances with us. Other players can come here to help us.
"We are being very, very demanding and we are first speaking about the possibility to sign very big, very expensive players."
Arsenal's only summer signing so far has been Brazilian teenager Gabriel Martinelli but the London club is targeting Saint-Etienne defender William Saliba – though north London rival Tottenham is also keen on the French 18-year-old.
Having missed out on Champions League qualification, the Gunners' transfer budget is thought to be as low as £40 million.
So far they have made an offer of £25 million for 22-year-old Scotland international Tierney, plus £40 million for 26-year-old Ivorian Zaha, who has four years left on his contract and is valued at about £80 million by Palace.
"I don't think Arsenal have actually made a bid that has come anywhere near our valuation," Palace boss Roy Hodgson told Sky Sports.
"I'm sure the player realizes that if someone's going to take him away from us, he'll expect clubs to pay the market value. Until someone does that, there's not much to discuss regarding Wilf."